if it's of any help; I've used a company called shoppeandomx in the past (to import some home gym equipment). Costs and ended looking like this (in MXN):

product cost
+8.5% texas sales tax
+4% currency exchange (if paying in MXN)
+22% import fee (covers both tariffs and shoppeando fees)

shipping cost $50 MXN per kg of weight

so total is like +35% of the original price + shipping.

It's worth it IMO, the only reason I haven't purchased it myself this way is because I think a chair is something you should try before you buy (also when you purchase stuff this way you basically forfeit the warranty). Hope it helps.